1. Field of the Invention
The present invention relates in general to the field of information handling system power management, and more particularly to information handling system dynamic fan power management.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling systems are built from a variety of components that consume electrical power and produce heat as a byproduct of their operations. Generally, information handling systems include some sort of active and/or passive thermal energy management to prevent excessive temperatures that can lead to system failure. Typical active thermal energy management includes attaching heat sinks to components that generate thermal energy and passing a cooling airflow over the heat sinks to remove the thermal energy from the information handling system. Generally, the larger the surface area of the heat sink and the greater the airflow rate used in an active thermal energy management system the greater the amount of thermal energy that is removed from the information handling system.
Although adequate thermal energy management for an information handling system is generally maintained with powerful enough cooling fans, other factors constrain the size of cooling fans available for a particular information handling system. One factor is the size of the housing of the information handling system. Larger housings generally have less impedance to airflow and more size to include larger cooling fans that generate greater cooling airflow. In contrast, smaller housings have greater impedance to airflow so that a given cooling fan tends to have less effectiveness than in a larger housing. In addition, smaller housings have less room for heat sinks so that less heat sink surface area generally leads to less effective thermal transfer for a given cooling airflow. Another constraint on cooling fan size and the number of cooling fans included in a housing is the power consumption by the cooling fans. Typically, an information handling system has a power supply with a maximum power output. In some instances cooling fan power draw varies between 5% and 25% of available power depending upon the thermal conditions within an information handling system housing.
Thermal energy management in multi-node information handling systems can present a complex problem due to the large variation in thermal conditions within an information handling system rack or other type of multi-node chassis. Multi-node server information handling systems often are designed to have a high density to increase the processing capability of systems deployed in valuable data center space. An information handling system rack may include a large number of server information handling systems in a dense arrangement that share power and cooling resources under the control of a chassis management controller (CMC). Thermal conditions within a rack can vary considerably based upon workload at different information handling systems. One difficulty with shared power and cooling resources is that a component or server node cooling request can result in a power draw for a cooling fan that causes a non-linear performance per Watt behavior for a rack. Essentially, a single component or server node can cause a much larger cooling fan speed response than is required by other components or nodes, which results in a relatively large cooling fan power draw that fails to provide a linearly-related decrease in thermal conditions within the rack. Another problem is that a component or server node cooling fan request can draw power that exceeds the power output of a rack power supply, resulting in power supply shutdown or performance impacts on other component or server node operations, such as CPU throttling or other component thermal management actions. In some systems, a fan speed maximum input to a single fan can map to other fans to go full speed resulting in high power consumption with relatively little improvement in thermal transfer from the system.